Arc-cathode production of titanium



y 1959 R. D. BLUE ET AL ARC-'CATHODE PRODUCTION OF TITANIUM Filed Feb. 15. 1957 INVENTORSL Robe/'1 0. B/ue Marsha/l 1Q Ne/ 'o er/ 6 TTORNE K5 M S'W ARC-CATHODE PRODUCTION or TITANIUM Robert D. Blue and Marshall P. Neipert, Midland, Mich, assignors to The Dow Chemical Company, Midland, Micln, a corporation of Delaware Application February 15, 1957, Serial No. 640,556 Claims. (CL 204-64) The invention pertains generally to the production of titanium metal. It pertains more particularly to a method T "ate'nt of and apparatus for the electro-deposition of titanium metal on a retractable arc-producing cathode from an impure titanium source.

Titanium metal has been produced largely by the chemical reduction of a titanium halide particularly titanium tetrachloride by metals more electropositive than titanium, e.g., magnesium. Titanium has also been produced in limited quantities by the thermal dissociation of a titanium halide, particularly titanium tetraiodide.

Some progress'has been made in the production of titanium at a conventional submerged cathode by electrolysis of a fused electrolyte comprising a halide or mixed halides of alkali or alkaline earth metals containing a lower halide of titanium. Neither a substantially pure halide nor the mixed halide salt, however, has been fully successful. When a bath of a single fused salt, e.g., NaCl, is employed as the electrolyte, temperatures of at least about 850 C. are required. Steel parts are clearly weakened when subjected to temperatures in that range. Therefore, any means for removing the titanium which employs moving steel parts requires elaborate cooling means. Cooling systems employing water as a cooling medium are usually employed. Such cooling systems are costly to design, construct, and maintain. Furthermore, the employment of a readily vaporizable material such as water in the proximity of hot titanium is very dangerous and definitely not recommended for commercial production.

Mixed fused salts. are not a satisfactory bath when employed in a conventional electrolytic cell having a submerged cathode becausewhen mixed fused salts are thus employed in proportions which permit lower temperatures, the titanium. is produced at the submerged cathode as a highly pyrophoric powder. Such highly pyrophoric material has but very small commercial value and constitutes a serious hazard to safety.

An object of the present invention is to provide an improved method of producing massive titanium metal electrochemically in a fused salt bath of mixed alkali or alkaline earth halides at lower temperatures than those heretofore found necessary.

Another object is to provide a method of producing titanium electrochemically in a fused salt bath of a substantially pure alkali or alkaline earth halide which permits the removal of the titanium thus produced by a continuous operation which does not require water-cooling means.

Another object is to provide a method of producing titanium employing a consumable anode of impure titanium in a bath of a fused alkali or alkaline earth halide or mixtures thereof containing a lower halide of titanium.

Another object is to provide a method of recovering substantially pure titanium by electrolysis on an arc-producing retractable cathode at the surface of the electrolyte.

A further object is to provide a method of producing ductile titanium metal by first reacting TiO, with carbon 2,887,443 P t t May 9,1259

and thereafter recovering the titanium from the thusprepared carbon-containing source by electrolysis in a fused salt bath. I J

A still further object is to provide a continuous method of producing titanium from a source containing at least percent titanium by depositing the titanium in a com pact flake form on a retractable cathode and periodically loosening and carrying away the thus-deposited titanium.

The method of attaining these and related objects is described and illustrated-hereinafter.

The invention comprises consuming an impure titanium anode by electrolyzing lower-valence halides-of titanium; e.g., titanium trichloride-or titanium dichloride, in a fused salt bath and recovering the titanium in a comparatively purified state by accretion on a retractable cathode :which is maintained-at such a distance above thebath that an arc is formed between the cathode and the surface 'of the bath. The cathode is gradually retracted as the accretion of titanium grows at the end thereof.

Fig. 1 of the drawing shows an elevational section of an apparatus suitable for practicing the invention.

Fig. 2 and Fig. 3 are modifications of portions of Fig. 1 showing alternative means for providing impure titanium for the electrolysis.

The fused salt bath consists essentially of an alkali or alkaline earth halide or a mixture thereof, e.g., NaCl or the eutectic mixture of KCl and NaCl. The eutectic salt mixture offers the advantageof low temperature operation. On the other hand, a substantially pure salt bath of NaCl, offers the advantage of providing a better formed and more nearly pure Ti accretion at the cathode. Either a divalent halide or a trivalent halide must be present in the bath as the titanium halide, the chlorides being the preferablehalides to employ. Available sources of the lower chlorides of titanium usually consist of mixtures of the triand dichlorides. The dichloride is preferred to the trichloride because it results in greater'current efficiency and a purer titanium recoverable at the cathode. After a convenient size titanium accretion, referred to hereinafter as a carrot, has formed on the cathode, it is further retracted, and the carrot is loosened by impact, vibration, or rod-sleeve arrangement, described hereinafter, and caused to fall from the cathode. An improved embodiment of the invention is to have a boat or pan which slides beneath the cathode end at the time that the carrot is loosened therefrom to catch the carrot and carry it to a place of storage.

The titanium may be provided by any source of titanium containing not less than 90 percent titanium and preferably not less than percent titanium. It may be in the form of an elongated stick or as a lump secured to a steel rod which serves as the positive terminal of the cell as shown in Fig. 1. On the other hand, it may be in comparatively small pieces confined in a basket of porous, perforated, or interwoven conducting material which is not itself affected by the electrolysis connected to a positive source of electricity; or the pot of the cell may be made the anode and pieces of impure titanium merely dropped into the pot.

A particularly useful embodiment of the invention is to prepare a carbon-containing titanium anode by an adaptation of known methods and thereafter to electrodeposit the titanium, from the anode in a fused salt bath containing a lower halide of titanium, on an arc-producing retractable cathode according to the invention.

Titanium. occurs plentifully as its oxide. A common method of winning metals from their oxides isby reacting theoxide with a reducing agent such as carbon. When titanium oxide is reacted with carbon, however, titanium carbides, particularly TiC, together with some crystal lized carbon in the form of graphite, and traces of other materials are present with the titanium metal. A workable and economically feasible method of winning the titanium from the carbide either alone or in admixture with graphite has been a long-felt need in the art of titanium production. On embodiment of the present invention provides sucha method.

A carbon-containing titanium anode suitable for this embodiment of the invention may be prepared by one of several known methods. A particularly Suitable method of preparing the anode for use in the invention is that described by H. Moissan in Compt. Rend, v. 117, pp 423-425, v. 120, p. 1393 and v. 125, p. 839. Sixteen parts of titanium dioxide and seven parts of .carbon by weight are reacted in an electric arcfor. minutes or longer. The principal reaction may be represented by theequation:

"The presence'of'a flux, e.g.,' upto'IO percent at Cal by weight, with-the carbon and TiO causes 'the'reduction of TiOgto proceed smoother and faster giving a better product. The carbon-containing titanium product may be formed in a desired'shape to serve'as an anode or thean'ode may be in the form of pieces which may be placed in a basket composed of a conducting material as explained hereinabove.

Titanium dichloride and titanium trichloride suitable for practicing the invention may be prepared according to known methods such as those set out in Titanium by Barksdale, pp. 81 to 82 (1949).

"Titanium dichloride and titanium trichloride may also be prepared according to our copending application, Serial No. 659,253, filed May 15, 1957, wherein a gaseous halogen compound such as TiCl HCl, HBr, or C1 is reacted with Ti sponge, or carbon-titanium alloys or TiC'to'produce TiCl and TiCl The moltensalt bath should have a melting point below about 700 C. The KCl-NaCl bath and particularly the eutectic mixture is preferred because of its lower melting point. The following melting point values for 'KCl-NaCl mixtures are given in molal percentages:

KClin NaOl 1n Melting Molal Molal Point, 0 percent percent 100 none 776 80 20 736 70 30 720 60 40 665 50 50 600 40 G0 686 30 70 697' 85 760 none 100 798 The "above table illustrates the lower operating temperatures possible when mixtures .of KCl and NaCl between 70 percent KCl-30 percent NaCl and 30 percent K'Cl-70 percent N'aCl, molal quantities, are used.

The 'TiCl or TiCl ormixture thereof, is added to the 'bath in such amount that the titanium fraction of the trichloride and/or dichloride comprises between 8 and 16 percent and preferably about 16 percent by weight. By the titanium fraction ismeant that portion of the titanium chloride which would be titanium if quantitatively analyzed. Toprovide thebath. with 1.6 percent of titanium .byfladding TiCl .about 5.1 percent of the weight-of the bath. of not, is added.

"The current densitytemployed at-the cathode is based upon that .necessary to attain the desired deposition temperature which isnbetween 850 C. and 1400 C. The temperaturemay be satisfactorily ascertained by employing. an optical pyrometer. A cathode current density o'f'between 40 and 350 amperes per square inch of cathode areaat'the arc is usually employed.

The voltageemployed, as measuredacross the terminals of the anode and cathode, is not critical .butis gen erally between 8 and 15 volts, although higher voltages may be employed. The amperage for a given voltage will vary according to the resistance offered. The resistance depends upon such conditions as the area and spacing of the electrodes and amount, type, and tempera tu're of the electrolyte.

Referring to Fig. 1 in. greater detail there is shown furnace setting 1. Heat is provided by gas burner 2. Outlet 3 provides for the escape of combustion gases. Pot 4, adapted to contain the fused bath to be electrolyzed, is positioned in the furnace setting. Pot 4 is provided with removable cover 5 which is secured to flanged rim 6 of the pot by means of electrically insulated bolts 7. Gasket 8 of electrically insulating material provides a seal between the cover 5 and rim 6. Water jackets 9 on the outside of cover 5 and rim 6 above and below the gasketcncircle the cellnearbolts 7 to prevent the heat in that area-from damaging the gasketand insulated bolts. Thermocouple 10 provides a continuous means of ascertaining the temperature of the bath. Anode chamber 11 is integrally secured in an upright position above the opening provided therefor in cover 5. Anode chamber 11 is equipped with evacuating line 12 and inert gas line 13 containing valves 14 and 15, respectively. The upper end of chamber 11 has secured thereto, by means of electrically insulatedbolts 16, removable cover 17 having a stufling box 18 therein through which is inserted anode rod 19 to which is secured impure titanium piece 20. Gasket 55 of insulation material prevents electrical contact between cover 17 and the walls of chamber 11. Projecting atright angles to chamber "11 are side-wall housings 21 and 22 in which gates 23 and 24 respectively, which have opposed mating slightly beveled edges, are moved by handles 25 and 26 to provide a closure means against air contamination through chamber 11 when adding impure titanium to anode rod 19. Housings 21 and 22 project also laterally into chamber 11 sufficiently to provide a rectangular opening therethrough when gates 23 and 24 are open. Packings 27 provide tight fits for handles 25 and 26. Gates 23 and 24 are rotatably positioned in brackets .29 and provide a means for forcing the forward portions of the upper faces of gates 23 and 24 against the upper face of housing -21 and 22 to prevent passage of gases between the gates and the side-wall housings when the gates are closed. The beveled edges'of the gates provide good contact between the mating edges when the forward ends of the gates are tipped slightly upward.

Flanged nipple 30 is integrally'fixed about the o'pening providedtherefor in cover 5. Cathode chamber 31, having its lower edge flanged to mate withflanged nipple 30, is" se'curedin an upright position to nipple 30 by means of bolts 32. Chamber 31 is provided with removable cover 33 secured by electrically insulated bolts 34 and electrically'insulated therefrom by gasket '56 of insulation material. Cover 33 has an opening therein which permits'the insertion therethrough of sleeve 37 in which cathode rod 36 is slidably positioned, Cathode rod 36 is provided with rack and pinion assembly 38 for advancing or retracting rod 36 independently of sleeve 37. Sleeve 37 is equipped with rack and pinion assembly 39 for raising or lowering sleeve 37. Cylindrical guide 40 provides a sliding support for sleeve 37. Inlet 41v is provided in cathode chamber 31 for admission of inert gas. Exteudingsfrom cathodechaniber 33a. is auxiliary chamber 42 which contains boat 43 provided with handle 44 extending horizontally through'stuth ing box 45 of auxiliary chamber 42. Extending dowrrwardly from auxiliary chamber 42 is drop chamber 46 having valve 47 therein and a flanged bottom edge. At tached to the flanged bottom edge is receiver 48 for receiving the contents of chamber 42 when valve 47 is opened.

Sight glass 49 extending through cover enables an operator to observe the operation of the cell.

In practicing the invention, using the apparatus illustrated by the drawing for example, the cell is charged with a suitable alkali or alkaline earth halide salt, as described hereinabove, to form electrolyte 50 which is maintained in the molten state. Inert gas is introduced through inlet 41 and exhausted at outlet 12 to flush the system.

Rod 19 is retracted so that its lower end is above housings 21 and 22. Gates 23 and 24 are then closed and inert gas introduced through line 13 and exhausted through line 12. Cover 17 is then removed and titanium bearing chunk 20 is secured thereto. Cover 17 is then replacedand, while continuing to introduce inert gas, gates 23 and 24 are opened and chunk 20 is immersed in bath-50 as'shown in Fig. 1. The upper end of rod 19 is connected to the positive terminal of a source of D0. electricity.

The negative terminal of the source of DC is connected to cathode 36 of the cell. lowered into electrolyte 50 and slowly retracted until it emerges from the surface of the electrolyte whereby an arc is struck between the cathode tip and the electrolyte. Cathode 36 is then withdrawn slowly to maintain the are at the desired temperature. Since the diand trihalides dissociate in solution into titanium and halide ions, at the instant the electric are forms across the gap between the cathode and the electrolyte titanium begins to accrete on the tip of the cathode at the arc. The halide ions react with unrefined or unpurified titanium metal at the anode to form more diand trihalides. The cathode is then slowly retracted or withdrawn so as to continue to maintain the are as the titanium continues to accrete thereon forming a massive accretion or carrot of a generally cylindriform shape on the end of the cathode. As the titanium carrot forms at the end of the cathode, the thus-formed carrot serves as a part of the cathode itself.

The size of the gap between the cathode tip and the surface of the salt is governed according to the temperature desiredinthe arc. The optimum temperature of the arc is that which results in the most consistent and uniform deposition or accretion of the titanium on the cathode and is usually between 900 and 1200 C.

The gradual withdrawal of the cathode is referred to as rise-rate. When the gap between the surface of the bath and the cathode is widened by. increasing the riserate of the cathode, the resistance and the temperature are increased. An increase in resistance is accompanied by an increase in potential or voltage across the gap. A temperature between 850 and 1400 C. is easily maintained by regulating the gap between the cathode and the surface of the electrolyte.

When a suitable arc has been formed, it is desirable Cathode 36 is then to maintain a more or less constant gap. The gap may be manually controlled or it may be controlled by automatic means, e.g., rack and pinion assembly 38 may be operated by a motor which is actuated by a relay system which transposes and amplifies an electrical impulse formed in response to a change in the voltage across the gap according to known means. For example, when the voltage across the gap has decreased to a predetermined value by the accretion of titanium on the cathode, the motor is actuated and moves cathode 36 upward to widen the gap.

The length of the titanium carrot'permitted to accrete on the cathode is not critical but carrots of k to 2 /2 inches long are convenient lengths in a small-scale operation. Cross-sectional dimensions of a carrot depend largely upon the shape and size of the cathode where deposition takes place. The cross-section of the carrot depends also on certain operating conditions such as the current density of the electrolyte and the temperature of the arc. As a general rule the carrot will ex- 6 ceed the cross-section of the cathode to some extent, such 'extentbeing somewhat greater when the rise-rate is relatively slow. A cathode which results in a carrot of $6 to'% inch across its largest cross-sectional dimension is usually employed when producing carrots of the length suggested above.

After producing the desired size of titanium carrot, the cathode is withdrawn sufiiciently to break the circuit, and the carrot dislodged from the cathode and removed from the apparatus. This may be accomplished by moving sleeve 37 downwardly with reference to cathode 36. The lower end of the sleeve 37 then pushes oft the carrot from the cathode. A recommended mode of recovering the carrot is to move boat 43 beneath the cathode tip, at the time the carrot is dislodged, to receive it. As shownQboat 43 containing thedislodged carrot iswithdrawn by means of handle '44 to a position.v While above chamber 46 in this position the boat is inverted to drop the'carrot into chamber 46. By opening valve 47 the carrot may be dropped into're- ,ceiver 48 without admitting-air to the system.

The invention will. be better understood by the 'fol-' lowing example. i

Example A rod-shaped ingot of carbon-containing. titanium material was prepared by arc melting TiC and metallic titanium. The titanium material thus prepared showed the following analysis in weight percent for the elements for .which an analysis was made, the balance being essentially titanium:

0 Al Fe Mn Mg Ni s1 Zr v 4.0 .023 11 .056 .002 Nil .08 .09

' of the molten KCl-NaCl bath. Air was flushed from the apparatus by admitting inert gas 52 through inlet 41. A cylindrical piece of the carbon-containing titanium thus prepared was secured to rod 19 to form anode 20 and placed in bath 50. Rod 19 was connected to the positive terminal of a source of DJC. electricity. Cathode rod 36 having a diameter of about /2 inch was connected to the negative terminal of the DC. source. At the tip of the cathode an arc was struck with the surface of bath 50 whereby a complete circuit was set up with a potential of 10 volts across the arc and a current of 41 amperes. The current density of the cathode was 350 amperes per square inch of cathode area involving the arc. Titanium metal-began to accrete at the end of the cathode to form carrot 51. As the titanium continued to accrete, the cathode was retracted slowly at an average rate of about 0.12 inch per minute. The temperature of the arc was about 900 C. as determined by an optical pyrometer. As titanium can-0t 51 accreted on the cathode, it formed an extension'of the cathode itself. The spacing was gauged by positioning .the cathode relative ,to the electrolyte surface ,at a height producing the most consistent and uniform-shaped titanium carrot.

Carrot 51 formed thereby was between and.% inch in diameter. When it was about 2 inches long, it was removed from the cathode by raising cathode 36, together with sleeve 37, so that carrot 51 was at a height greater than that of boat 43 thereby also breaking the circuit across the gap. Boat 43 was advanced by means of handle 44 to a place beneath the carrot and the cap '7 rot was dislodged by manual operation as explained hereinabove.

The means employed for removing the carrot need not be manually operated but may be operated by a synchronized mechanism, not shown. The mechanism may be operably geared to an electric motor which is ener- 'gized when a contact switch is tripped by cathode 36 at a predetermined height or when the resistance through the carrot has increased to a predetermined value. The sequence of steps thus automatically operated are substantially the same as those in the manual operation above.

'The titanium metal deposits formed on the'cathode were separated from adhering salt by volatilizing oif the 'salttu'nder a vacuum according to known practice. The titanium then contained the following elements in percentvby weight for which an analysis was made, the balance being titanium containingnot more than 0.001 perdent or other impurities:

.016 .021 .120 .060 .00l Nil .002 (.01

The example illustrates but one mode of practicing the invention. Any titanium source containing at least 90 percent metallic titanium may be employed as the anode. Other modes of practicing the invention are il- 'lustrated in Figures 2 and 3. Figure2,illustrates the use of fragments 60 of impure titanium which are placed in basket 61 of a conducting material which is not affected by the electrolysis. Basket 61 is made the anode of a suitable cell as indicated by the dotted outline in Fig. 1 below the anode chamber. The titanium is recovered from the fragments on subjectingthem to electrolysis in the molten electrolyte employing the principle of the invention. In practicing the invention in this manner, a steel basket, for example, is connected to a positive lead-in line as indicated by the dotted line passing upward to and through stufiing box 18 in place of rod'19.

Fig. 3 illustrates a mode of practicing the invention wherein steel pot 4a is shown directly connected to a positive source of electricity and titanium particles 60a are added directly to the molten salt bath 5011 in the 'pot. Particles 60a together with pot 4a serve as the anode of the cell. In the modification shown in Fig.

3, cover 5a is completely insulated from the body of pot 4a by insulation 62 and secured thereto'by electrically insulated bolts 16a. Opening 63, having cover 64 thereon, provides a means for adding impure titanium particles 60a. No anode chamber is required in this modification.

As a further modification, lower-valence halides of titanium may be fed directly into the electrolyte during operation of the .cell to maintain a source of titanium instead of the lower-valence halides being provided, after operation has begun, as hereinabove described from an impure titanium anode reacting with halide ions in the bath.

These and other modifications of the invention will be construed as falling within the purview of the invention as defined by the claims.

A number of advantages in theart of. producing ti- --'taniu'm are realizable froma practice of theinvention. Among such advantages are: the production of titanium metal in'a cohesive massive form, in contrast to pyrophoric powder, at a temperature of not over about 700 C., eliminating the need for cooling systems to cool moving mechanical parts and the accompanying explosion' hazard; a method of continuous electrolysis'of lower halides of" titanium in a fused salt bath to produce timetal from which the'bath' may be subsequently easilyseparated by'sublimation' and the titanium thereafter melted into ingots; a means of utilizing carboncontaining titanium anodeswhich are made by reacting carbon and Ti0 thereby rendering such extensive sources of titanium as rutile, Sorel titaniferous by-product slag, and ilmeriite more readily utilizable as direct sources of titanium metal.

Having thus described the invention, what is claimed and desired to be protected by Letters Patent is:

1.The method of producing ductile titanium which comprises charging an electrolytic cell with a halide salt bath mixture consisting of a halide salt selected from the class consisting of the halides of alkali and alkaline earth metal halides-and mixtures thereof and with lowervalence titanium halides in an amount between 8 and .16 percent by weight of' the titanium fraction provided by' said titanium halides based on the weight of said bath, making the anode of said chamber an impure titanium metal consisting of .at least percent titanium and the cathode a retractable conductor, creating an'arcbetween the surface of said salt mixture and the retractablecathode, collecting ductile titanium on the cathode, gradually retracting the cathode while maintaining the arc, and thereafter recovering the titanium thus collected.

2. The method according to claim 1 wherein the salt bath comprises a mixture of potassium chloride and sodium chloride in substantially eutectic proportions.

3. The method accordingto claim 1 whereinthe halide of said salt bath is the chloride and the lower-valence titanium halide is predominantly the dichloride.

4. The method according to claim 1 wherein the anode of the cell is a chunk of titanium-bearing material containing at least 90 percent titanium.

5. The method according to claim 1 Whereinthe source of titanium is fragmented titanium sponge confined in a conducting basket, having openings therein, which serves as the anode of the electrolytic cell.

6. The method according to claim 1 wherein the elec trolyte container of the cell is made an anode of the cell and the source of titanium is fragments of titaniumbearing material containing at least 90 percent titanium unconfined in the fused salt electrolyte andin direct contact with said container.

7. The method of producing titanium metal from an oxide of titanium which comprises reacting the oxide With carbon to form a carbon-containing titanium solid shape, containing at least 90 percent titanium, making said shape an anode in a molten salt electrolyte consisting essentially of halides of alkali and alkaline earth metals and at least one lower-valence halide of titaniumin sufficient amount to yield between 8 and 16 percent by weightof the titanium fraction, positioning a cathode at the surface of said electrolyte to form an arc therebetween, collecting titanium metal on said cathode, gradually with drawing said cathode and the thus collected titanium metal while maintaining said are, continuing. to collect titanium on said cathode, and removing the thus collected titanium therefrom.

8. The method of producing titaniummetal from an oxide of titanium which comprises reducing the oxide with carbon to form carbon-containing titanium solid pieces, containing at least 90 percent titanium, placing said pieces in a basket of conducting material, making said basket an anode in a molten salt bath selected from the class consisting of an alkali halide, an alkaline earth halide, and mixtures thereof, and containing atleast one lower-valence halide of titanium, forming'an are between a retractable cathode and the surface of the molten salt bath, so as to produce a deposit of titanium on the cathode while gradually retracting the cathode so as to maintain the are as the deposit forms, periodically withdrawing the cathode having the titanium thereon sutficiently to break the arc, and dislodging's'aid titanium.

9. The method according to claim 8 wherein the salt bath is substantially the eutectic mixture "of potassium chloride and sodium chloride containing a mixture of titanium dichloride and titanium trichloride in an amount suflicient to provide between 8 and 16 percent by weight of the titanium fraction of said chlorides at a temperature of not over 700 C.

10. The method according to claim 7 wherein the salt bath is sodium chloride containing a mixture of the lower valence chlorides of titanium, said mixture comprising predominantly titanium dichloride.

References Cited in the file of this patent UNITED STATES PATENTS Buck et a1. Feb. 14, 1956 Schultz et a1. Feb. 14, 1956 Alpert et a1 Apr. 10, 1956 Mellgren May 29, 1956 Raynes et a1 Nov. 12, 1957 OTHER REFERENCES Journal of Metals, September, 1956, pages 1162-1168. 

1. THE METHOD OF PRODUCING DUCTILE TITANIUM WHICH COMPRISES CHARGING AN ELECTROLYTIC CELL WITH A HALIDE SALT THE CLASS CONSISTING OF THE HALIDES OF ALKALI AND ALKALINE THE CLASS CONSISTING OF THE HALIDES OF ALKALI AND ALKALINE EARTH METAL HALIDES AND MIXTURES THEREOF AND WITH LOWERVALENCE TITANIUM HALIDES IN AN AMOUNT BETWEEN 8 AND 16 PERCENT BY WEIGHT OF THE TITANIUM FRACTION PROVIDED BY SAID TITANIUM HALIDES BASED ON THE WEIGHT OF SAID BATH, MAKING THE ANODE OF SAID CHAMBER AN IMPURE TITANIUM METAL CONSISTING OF AT LEAST 90 PERCENT TITANIUM AND THE CATHODE A RETRACTABLE CONDUCTOR, CREATING AN ARC BETWEEN THE SURFACE OF SAID SALT MIXTURE AND THE RETRACTABLE CATHODE, COLLECTING DUCTILE TITANIUM O N THE CATHODE, GRADUALLY RETRACTING THE CATHODE WHILE MAINTAINING THE ARC, AND THEREAFTER RECOVERING THE TITANIUM THUS COLLECTED. 